1. Field of the Invention
The present invention relates generally to avionics, and more particularly an integrated communications management unit and very high frequency data radio.
2. Related Art
The growing volume of air traffic worldwide is forcing air traffic control systems to become ever more sophisticated. For example, a large effort is underway to allow for xe2x80x9cFree Flight.xe2x80x9d Free Flight is an innovative concept designed to enhance the safety and efficiency of the National Airspace System (NAS). The concept moves the NAS from a centralized command-and-control system between pilots and air traffic controllers to a distributed system that allows pilots, whenever practical, to choose their own route and file a flight plan that follows the most efficient and economical route. The emerging world of free flight promises operators tremendous benefits in both time and cost savings.
Any such advance in air traffic control will be dependent upon a high volume of information flowing between air traffic controllers and aircraft, and aircraft to aircraft. Timely and accurate information exchange is critical to the airlines operation. An efficient communication link is therefore of critical importance to future air traffic communications and management. With the rapid expansion of airborne data link requirements, the existing communications network is being stretched beyond capacity.
The Aircraft Communication Addressing and Reporting System (ACARS) VHF data link was established in 1978. Many airlines depend on the ACARS data link for efficient, cost-effective operations. Though ACARS has evolved significantly over the years to cope with additional requirements, its limits are being reached. In the future, the data link environment is expected to evolve toward the Aeronautical Telecommunications Network (ATN).
The avionics systems within the aircraft must be able to keep pace with this increased flow of information. For example, the on-board radios will be required to handle the increased digital message traffic as well as voice communications. The design of avionics systems are in some ways constrained by industry-wide standards, such as those standards promulgated by Aeronautical Radio, Inc. (ARINC). ARINC is the technical, publishing and administrative support arm for the Airlines Electronic Engineering Committee (AEEC). The AEEC was formed in 1949 and is considered to be the leading international organization in the standardization of air transport avionics equipment and telecommunication systems. ARINC standards define the design and implementation of everything from testing requirements to navigational systems to in-flight entertainment.
Different ARINC standards address various aspects of the air-ground data link and the radios on-board the aircraft. ARINC 716/750 specifies the form, fit and function for a Very High Frequency (VHF) data radio capable of VHF voice and data communications. VHF refers to the frequency band between 30 MHz and 88 MHz, and 118 MHz and 137 MHz, which is used for line of sight commercial/civilian aeronautical applications.
The communications management unit refers to avionics equipment for managing the communications element of Communications, Navigation and Surveillance/Air Traffic Management (CNS/ATM) on-board the aircraft, including selection of the means of air-ground communications in a particular environment. ARINC 758 specifies a communications management unit which operates as a bridge/router to transfer data link messages over satellite, VHF, HF, and SATCOM data link mobile air/ground communications networks.
Currently, the VHF data radio and communications management unit are housed in separate enclosures within the aircraft. These units communicate with one another over a standard bus interface. Generally, three specifications defined the characteristics of avionics buses: ARINC 419, ARINC 429, and ARINC 629. ARINC 419 is the oldest and is considered obsolete. ARINC 629 is the newest, though only the Boeing 777 currently employs this interface. The vast majority of avionics terminals employ the ARINC 429 interface.
ARINC 429 defines the standard for the transfer of digital data between avionics systems. ARINC 429, formally known as the MARK 33 Digital Information Transfer System (DITS) specification, contains three parts in the current release of the specification (ARINC 429-15). Unlike the 419 specification, ARINC 429 defines a particular bus design and is implemented widely across virtually all modern ARINC line replaceable unit (LRU) systems. The ARINC 429 specification provides the electrical, timing, and protocol requirements. The ARINC 429 is implemented as a simplex, broadcast bus, with a wiring topology that is based upon a 78 ohm, unbalanced, twisted shielded pair. According to ARINC 429, actual transmission rates may be at a low or high-speed of operation: 12.5 kHz (12.5 to 14.5 kHz) and 100 kHz (+/xe2x88x921%).
Current radio systems having separate enclosures for the VHF data radio and communications management unit communicate via an ARINC 429 interface and are therefore limited to a throughput of 100 kbits per second (Kbps). These radio systems have difficulty keeping up with the volume of messages being sent over the current ACARS system, resulting in messages having to be resent when they are dropped. Future ATM systems will only demand higher throughputs. The architecture of current radio systems, given their reliance on the low-throughput ARINC 429 interface, are not easily adaptable to satisfy the communications needs of future ATM systems.
A need therefore exists for an improved avionics communication system having a high throughput and adaptable to the demands of future ATM systems.
Briefly stated, the present invention is directed to a system for air-ground and air-air communications wherein a VHF data radio is coupled to a high-speed bus. The VHF data radio complies with the ARINC 716/750 standard and is accessible via the bus using a programmable interface. A communications management unit can also be coupled to the high-speed bus, which communicates with the VHF data radio via the bus according to the programmable interface.
Using a high-speed bus to access the VHF data radio as compared to using an ARINC 429 results in more efficient use of the airborne network because incoming messages can be processed faster with fewer errors, fewer messages are dropped, better error checking is possible, and messages may be routed to displays and intercoms more efficiently.
Another advantage of the current invention is that a programmable interface is used within the VHF data radio for communications over the high-speed bus. The programmable interface can be updated by loading new software as message protocols and formats evolve over time, without requiring any change in hardware.
An additional advantage of the current invention is that the communications management unit and VHF data radio can be housed within one enclosure. This reduces system cost, as well as space, weight and power requirements. Further, processing functions of the communications management unit (CMU) and the VHF data radio may be incorporated within a single card that can be accessed via the high-speed bus. Also, multiple VHF data radios may be housed with the CMU.